Got electronics you want to power up in the car? The Cobra CPI 480 400-Watt Power Inverter ($54.95 list) lets you do just that—and it's easier to use than you'd think. It converts low-voltage DC (direct current) battery power from your car's cigarette lighter to 115V AC (alternating current) household power. It's ideal for cars, trucks, RVs, tractors, and boats—assuming you get a unit that holds up, that is. We had some trouble with two of our three review units.

Editors' Note (5/24/12): A second of our three test units failed in a different car, leading us to believe our first unit's failure may not have been an anomaly. Cobra has some issues to address with the CPI 480's overall reliability. We have revised our rating downward from 3.5 to 2.5 as a result.

Features and DesignCobra claims the CPI 480 can power laptops, 13-inch TVs, DVD players, cell phones, and video game consoles. It's also capable of running an electric can opener, electric knife, a blender, and a food processor, plus some smaller power tools like a 7.2V cordless drill charger and a hot melt glue gun. For a complete list, check out Cobra's product page. Short of a microwave or coffee maker, or anything that generates an unusually high power surge on startup, the CPI 480 should deliver all the electrical current you need for most situations.

Design-wise, the Cobra CPI 480 is a brick. That's okay, because it doesn't need to be pocketable—just portable. It measures 6.5 by 4.2 by 2.6 inches (HWD) and weighs two pounds. It's made of a mix of aluminum and black plastic, and feels solidly constructed. It features two separate AC outlets on the back, plus a USB port for charging a phone, iPod, or other small device. There are semi-circle indents near all four corners, which let you mount the CPI 480 to a hard surface inside your vehicle using four screws, although none are included in the box.

A two-foot DC cord connects the CPI 480 to your vehicle's power jack. Although the CPI 480 is rated for 400 watts, and can handle short peaks of up to 800 watts, it only supports up to 150 watts when plugged into a cigarette lighter jack. For higher loads, Cobra includes a pair of two-foot, direct-to-battery, 12-gauge cables.

Performance and ConclusionsAs part of our Fastest Mobile Networks 2012 project, we tested three Cobra CPI 480s. We used each one to power eight cell phones simultaneously, all of which sat in the back of three 2013 Ford Taurus sedans. To do this, we used two Power Squids, each with four cell phones attached, and then plugged each Squid into one of the AC jacks on the CPI 480. Then we plugged the CPI 480 into either of the Taurus SHO's accessory power outlets, depending on what we were doing (there's one in the front and one in the back seat). The total load from the phones worked out to about 100 watts.

The CPI 480 features two LEDs: A green one indicating steady power, and a red one that lights up under overload conditions. During current overload, the red light will blink continuously before the unit shuts down. Under DC input voltage overload, the light turns on and the unit shuts down immediately, but it will keep checking to see if there's enough voltage to start up again.

Unfortunately, one of our three CPI 480s failed after just two days. The one I was using began sounding its high-pitched alarm. First, it did that a few times with the phones plugged into it. But eventually, it would do that all on its own, with nothing plugged in at all, and within 15 seconds of powering it on. In addition, while in use, the tiny fan on the back side of the unit kept powering up and down, almost like clockwork. Every 20 seconds or so, I'd hear a whirr for a few seconds, and then it would stop. Other times during the day, it didn't do that at all. A replacement Enercell 350-watt unit we bought from Radio Shack ran its fan the entire time, but also proved 100 percent reliable. Then a week later, a second Cobra CPI 480 unit failed on a different person in a different car.

While the Cobra CPI 480 lists for $54.95, I've seen it on Amazon for as low as $26. That's a pretty low price for something so useful. That said, two catastrophic failures within two weeks diminished my confidence in the product. That makes it tough to recommend, at least without a qualification that you buy one from a store with a liberal exchange policy, in case you get a defective unit out of the box. With that caveat, the CPI 480 does the job it's asked to do—as long as you get a good one.

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Jamie Lendino is the Editor-In-Chief of ExtremeTech.com, and has written for PCMag.com and the print magazine since 2005. Recently, Jamie ran the consumer electronics and mobile teams at PCMag, and before that, he was the Editor In Chief of Smart Device Central, PCMag's dedicated smartphone site, for its entire three-year run from 2006 to 2009. Prior to PCMag, he was a contributing editor for Laptop and mediabistro.com. His writing has also appeared in the print editions of Popular Science, Electronic Musician, and Sound and Vision,...
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